1. Field of the Invention
This invention relates to a method for detecting defects in a measurement means of a biochemical analysis apparatus, with which specific constitutuents in liquid samples are analyzed chemically. This invention particularly relates to a method for detecting defects in a measurement means of a biochemical analysis apparatus wherein a droplet of liquid sample is applied to an analysis medium, such as a chemical analysis slide or test film, containing a reagent which reacts with the liquid sample, and the optical density, which depends on how much of a reaction product was formed by the reaction between each liquid sample and the reagent in each analysis medium, is found.
2. Description of the Prior Art
Qualitative or quantitative analyses of specific chemical constituents in liquid samples are conducted for various industrial purposes. Particularly, it is very important in biochemical and clinical fields to be able to quantitatively analyze certain chemical or physical constituents in body fluids such as blood or urine.
Recently, as disclosed in, for example, U.S. Pat. Nos. 3,992,158 and 4,292,272, dry type chemical analysis slides were developed for use in systems designed for performing quantitative analysis, with which systems the concentrations of specific chemical constituents or specific physical constituents contained in a droplet of liquid sample, which is applied to the chemical analysis slide, are determined. It is possible to analyze a liquid sample more simply and more quickly with methods in which chemical analysis slides are used than with methods in which conventional wet type analyses are carried out. Therefore, it is more desirable to use chemical analysis slides, particularly in medical organizations, research laboratories, or the like, where many samples must be analyzed, than to carry out conventional wet type analyses.
In order for a chemical analysis slide to be used in the determination of the concentration of a specific constituent contained in a liquid sample, a measured amount of the liquid sample is put on the chemical analysis slide and is kept at a predetermined temperature (i.e. incubated) for a predetermined time in an incubator, which causes a color reaction. The chemical analysis slide is then exposed to light having a wavelength which is selected in advance. The selection of the wavelength depends on the kind of the chemical analysis slide (or the constituents of the liquid sample and the constituents of a reagent contained in the reagent layer in the chemical analysis slide). Light is thus irradiated to a reaction product which forms on the chemical analysis slide, and the amount of light reflected by the reaction product is measured. The optical density of the chemical analysis slide is then found from the measured amount of reflected light.
Also, as a means with which liquid samples can be automatically and sequentially analyzed, a novel apparatus is proposed in, for example, U.S. Pat. No. 3,526,480. In the proposed apparatus, a long tape-like test film containing a reagent is used instead of the aforesaid chemical analysis slides, and the application, incubation and measurement of samples are carried out sequentially on adjacent portions of the test film.
In general, in the biochemical analysis apparatuses utilizing the analysis media, such as chemical analysis slides or test films, many kinds of analysis media are used depending on what the specific constituent to be analyzed is. In such cases, light having different wavelengths should be prepared depending on the kind of the analysis medium, i.e. what the specific constituent to be analyzed is. In many cases, for this purpose, only a single light source is used, and light produced by the light source is selectively passed through one of a plurality of interference filters. In this manner, light having different wavelengths can be obtained.
The accuracy of the biochemical analysis utilizing the analysis media, such as chemical analysis slides or test films, is adversely affected by defects in the measurement means of the biochemical analysis apparatus. The defects in the measurement means include a change in the amount of light produced by a light source (lamp) due to deterioration of the light source with the passage of time, and a change in the absorbance or the transmission characteristics due to deterioration of interference filters with the passage of time. The defects also include a deviation in position of a probe, a filter wheel, or the light source.